The tables at Cafe Baroque near Covent Garden in London have supported lots of chess boards - it is a well known haven for casual pawn- pushers - but none has looked so strange as the one William Gramolt brought in recently.

Mounted on a Corinthian column, the Chessball resembles a black and white enamelled globe, marked off in lines of latitude and longitude. From their starting positions on opposite sides of the sphere, magnetic bishops and knights poke out like the spines on a Second World War naval mine.

There are almost twice as many spaces as an ordinary board, but the same number of pieces, and it is, its creator believes, a far more attacking game.

Mr Gramolt, a management consultant from Hartfield, East Sussex, hopes this latest variation on the ancient game of chess will make him rich. "I wanted to put what I preach into practice," he says. "I wanted to put together the optimum business."

But he faces a tough battle. British Grand Master Nigel Short believes variants have little appeal."History is littered with people trying to improve it, but chess is a very rich game, almost infinite in its complexity."On this, Mr Short is at odds with the former world champion Bobby Fischer, who recently launched a variant called Fischerandom, in which the back row pieces are placed on the wrong squares.

The Encyclopedia of Chess Variants by David Pritchard lists 1,450 modifications, from three- dimensional chess to four- player chess, with pieces from wildebeests to nuclear warheads. There are five spherical chess boards listed. Not one of them took off.

John Wareing, owner of The Chess Shop near Olympia, says he only has one variant available. "I've got Tri-Chess for three players, and I used to have Three-Dimensional chess. But it's quite a specialised interest."

Mr Gramolt was inspired to create his new board on a ferry crossing from Newhaven to Dieppe in 1985. He and his son played battleships on the red and white gingham tablecloths. "The following morning I had Chessball on my mind."

Mr Gramolt is offering his new game to mail-order customers for pounds 149, or pounds 129 during an introductory offer.

He says: "I know there are chess people so obsessed they wouldn't want to waste their time with anything else. But I wouldn't want Chessball to be killed off by someone saying 'It's not real chess'."